Methods to improve or alter the visual and tactile properties of yarn, fibers, filaments and the like are known in the art. Many such methods employ additives such as TiO.sub.2 and ZnS. U.S. Pat. No. 5,478,878 discloses a polymer composition comprising a polyphenylene ether, a polyamide and an inorganic filler including zinc sulfide and a photobleachable organic dye or pigment. Known techniques, however, are generally directed to using zinc sulfide as a phosphorescent agent or titanium dioxide as a delusterant. Following is a brief synopsis of known methods of incorporating various additives and fillers to fiber-forming polymers during processing into fibrous products.
U.S. Pat. No. 5,674,437 discloses luminescent fibrous material made from a composition comprising a thermoplastic polymer and a metal aluminate oxide pigment, whereas, U.S. Pat. No. 5,321,069 discloses phosphorescent and fluorescent articles prepared from a composition containing a thermoplastic polymer (e.g. polypropylene), a wetting agent and a phosphorescent agent such as zinc sulfide. The literature also includes the following patents of general interest: U.S. Pat. No. 5,750,616 discloses compositions comprising a thermoplastic resin, a fiber reinforcing material and carbon black; U.S. Pat. No. 4,331,776 discloses polyamide masterbatches made from polyamides and pore-forming agents; U.S. Pat. No. 4,719,066 discloses a method of making flame retardant polyamide fiber from polyamide and polyamide masterbatch comprising zinc, molybdenum and chlorine; U.S. Pat. No. 4,111,905 discloses compositions comprising a thermoplastic resin, zinc sulfide and optional basic compounds to prepare fibers with improved flame retardancy; U.S. Pat. No. 5,240,980 discloses opacifier compositions comprising a thermoplastic resin and zinc sulfide; U.S. Pat. No. 5,405,905 discloses compositions comprising a thermoplastic resin and a non-toxic phosphorescent pigment such as zinc sulfide; U.S. Pat. No. 5,443,775 discloses pigmented compositions comprising a thermoplastic resin and zinc sulfide; U.S. Pat. No. 5,478,878 discloses compositions comprising a filled thermoplastic resin, the filler being zinc sulfide; U.S. Pat. No. 5,674,437 discloses compositions and luminescent articles comprising a thermoplastic resin and zinc sulfide; U.S. Pat. No. 4,211.813 discloses photoluminescent compositions comprising a thermoplastic resin, zinc sulfide and a fluorescent material; U.S. Pat. No. 5,276,080 discloses compositions comprising a thermoplastic resin and semiconductive fillers; U.S. Pat. No. 3,988,108 discloses compositions to prepare colored structures, the compositions comprising a coloring agent and a prepolymer of a synthetic resin; U.S. Pat. No. 5,898,059 discloses a process to prepare polyethylene terephthalate ("PET"); U.S. Pat. No. 5,654,096 discloses electroconductive articles prepared from compositions comprising a thermoplastic resin and an electroconductive filamentary segment; U.S. Pat. No. 5,690,922 discloses deodorizable fibers made from a fiber incorporated with titanium dioxide, a phosphate of a tetravalent metal and a hydroxide of a divalent metal.
Known fiber-forming methods using TiO.sub.2 are expensive. Furthermore, such methods lead to abrasive articles since TiO.sub.2 is an abrasive material. ZnS, on the other hand, is a softer material; however, it is photocatalytic. The photocatalytic property of ZnS leads to discoloration or yellowing. Therefore, while methods employing ZnS instead of TiO.sub.2 to provide properties such as fluorescence and phosphorescence are known, using ZnS as a delusterant to improve the luster and abrasive properties of fibrous articles has not been reported.
There is a perceived need in the industry for fibers, filaments, yarn and like articles which have reduced discoloration, i.e. improved whiteness. Additional benefits of the articles of the present invention include reduced abrasiveness and static, and better hand as described hereinafter.